Sports Medicine: Just the Facts

CHAPTER 81 • BICYCLING INJURIES 481

• Mountain biking
  
  
  1. Downhill: Steep downhill race where focus is on
     speed. Injuries may occur as safety is sacrificed for
     speed.
  
  
  2. Dual slalom: Two racers compete in downhill ski-
     style slalom course.
     •Touring: Road riding for recreation typically over
     long distances. Rider may be loaded or nonloaded
     with panniers/saddlebags.
  
  
  
  


• Cyclocross: Off-road race in which riders complete a
  short (1–2 mi) lap multiple times in a set time period.
  Obstacles are present requiring the rider to mount,
  dismount, and carry cycle over the course.


• BMX/Trick cycling: Riders compete on ramps with
  stairs and railings, with multiple aerial stunts. High
  risk for injury with aerial acrobatics.
  
  
  1. Fastest growing segment of U.S. cycling with more
     than 60,000 riders
  
  
  2. Largest portion of child cyclists (Grubb, 2003)
  
  
  
  

FRAME TYPES

• Standard road: Traditional upright geometry with top
  tube parallel to ground


• Compact road: Sloping top tube allows rider to fit to a
  smaller frame, this maximizes stiffness and minimizes
  weight.


• Mountain/Hybrid: Flatter geometry, heavier bicycle,
  may have suspension to absorb shock.

FIT

• May be done at a bike shop with Fit Kit or “Size
  Cycle” (Christiaans and Bremner, 1998).


• Best frame size for a cyclist is as small vertically as
  possible, with enough length horizontally to allow a
  stretched out, relaxed upper body. This frame will be
  lighter and stiffer and handle better. (See Fig. 81-1)
  (Colorado)

FRAMESIZE
•To ensure proper frame size of bicycle, rider should
straddle top of the bicycle wearing riding shoes.

1. Road bikes:
   a. Standard geometry: 1–2 in. between the crotch
   and the top tube
   b.Compact geometry: Size determined by top
   tube length/reach (see below)


2. Mountain bikes: Determined by reach (see below)
   3.Calculations exist to determine frame size
   (Colorado):
   a. Inseam height (cm) ×0.67
   b.Mountain bike: Inseam =10–12 cm

SEATHEIGHT

• Optimal saddle height has been estimated based on
  maximal power output and caloric expenditure
  (Burke, 1994).
  1.Calculate height, which will be within a centimeter of
  0.883×inseam length, measured from the center of
  the bottom bracket to the low point of the top of your
  saddle. This allows full leg extension, with a slight
  bend in the leg at the bottom of the pedal stroke.
  2. When seated on bike with pedal at the 6 o’clock
  position there should be 25–30% flexion in the
  knee.
  3. Alternatively, the seat may be raised until the hips
  rock with pedaling, and then lowered until the
  rocking disappears.

SADDLEPOSITION

• Check the position of your forward knee relative to
  the pedal spindle—for a neutral knee position, you’ll
  be able to drop a plumb line from just below the front
  of the forward kneecap, and have it bisect the pedal
  spindle and ball of your foot below. “Keep Over Pedal
  Spindle (KOPS)” (Burke, 1994)

TOPTUBELENGTH

• The ideal position varies here more than anywhere
  else for cyclists, depending on riding style, flexibility,
  body proportions, and frame geometry, among others.
  And, your upper body position will evolve with more
  hours in the saddle.
  
  
  1. May be measured by placing your elbow at the fore
     end of the saddle—your outstretched fingers
     should touch the handlebars.
  
  
  
  

FIG 81-1 Bike frame dimensions.